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Quality seed production in rice and maintenance of viability of stored seeds

  • Ensure that the seeds for further multiplication are either from a research station or government farm or recognized seed producers.
  • The land used for seed production should be free from volunteer plants of other varieties grown previously.
  • To ensure genetic purity, a minimum isolation distance of 3 m from other varieties may be given in the field. Harvesting for seed purpose can also be done leaving a border row of 3 m within the field.
  • Rogue diseased plants, weeds and off-types in time.
  • Line planting facilitates, roguing and giving alleyways of 30 cm after every 3 m planting helps in manuring, plant protection operations and supervision.
  • Drain water at least one week before harvesting to ensure that the plants attain equal maturity at harvesting. Harvest the crop when 80% of the grains in a panicle are mature (at physiological maturity).
  • During summer months, ensure that the plants get sufficient water at dough stage till maturity.
  • Thresh the sheaves on the same day of harvest, as seeds of heaped sheaves may not perform well.
  • Dry seeds properly and ensure that the moisture content is not more than 13 per cent. Avoid excess drying in summer months especially short duration varieties as it reduces the period of viability.
  • While drying and storing, avoid contamination from yards or through baskets or bags.
  • Seeds may be stored in damp proof situations for avoiding absorption of moisture from atmosphere thereby losing viability early.
  • Polythene bags of 700 gauge or double gunny bags may be preferred for storing. Polythene bags of 400 gauge density may be preferred for storing paddy seeds dried to 10% moisture content or less.
  • Never stack seed bags in open floors. Store on pallets or wooden benches. The benches should be 30 cm away from wall and floor for proper aeration.
  • Never pile more than eight bags in a stack. This should be limited to three bags if the seeds require further drying.
  • Avoid storing plant protection chemicals, herbicides, fertilizers, etc. in seed store.
  • Fill up the cracks and crevices of store room by cementing to make it rat proof.
  • Spray 2% malathion solution in the godown before storing seeds to check insect pests.
  • Place pieces of cloth dipped in neem oil between stacked bags or neem oil cake covered in cloth bags inside seed bags to ward off pests.
  • Test seed germination at monthly intervals if the seeds are to be stored for more than eight months.
  • The viability of short duration varieties can be extended for a further period of 2-3 months at 80% level if the seeds are soaked for four hours in water and re-dried in shade, back to original weight at 13% moisture content. Seeds of short duration varieties like Jyothi and Triveni of virippu crop reach this level of germination 9-10 months after harvest and that of mundakan 8-9 months after harvest when stored under ambient conditions.
  • To keep sprouted pokkali seeds viable for two weeks, sprouted, the seeds are to be kept in baskets made of plaited coconut leaves lined with koova, banana, karingotta or teak leaves.
Seed rate

Transplanting              60-85 kg/ha

Broadcasting               80-100 kg/ha

Dibbling                      80-90 kg/ha

The above seed rates are specified for farmers' field on the basis of minimum germination of 80%. In pokkali  cultivation, for Vyttila varieties, 100 kg/ha may be sown on the beds or mounds formed in the field.

Seed rate may be enhanced from 80-100kg/ha to 125 kg/ha for Kuttanad, provided excess plants are removed in order to maintain optimum plant population

Seed treatment

Dry seed treatment

Dress seeds with P. fluorescenes @ 10 g/kg of seeds before sowing or with the following fungicides on the previous day of sowing (12 to 16 hours ahead) at dosage given below:
1. Carbendazim 2g per kg of seed

Wet seed treatment

Soak seed for 12 to 16 hours in a solution of P. fluorescenes @ 10 g/litre of water per kg of seed or Carbendazim 2 g / kg of seed per litre of water and drain to induce germination.

Treatment with the Carbendazim will protect the seedlings from blast disease up to 30 to 60 days after sowing.

The above seed treatment can also be used for giving protection from seedling blast in endemic areas.

Soak paddy seeds in CuSO4 (0.25%) and ZnSO4 (1%) solution for 24 hours. Drain and keep for sprouting. For soaking 1 kg of seed, 1 litre of micronutrient solution would be needed.

Nursery

For transplanting, healthy seedlings have to be raised in seedbed. Healthy seedlings can cope up better with the field conditions that affect the growth of young rice plants. Adopt wet or dry method for raising seedlings. The choice depends primarily on the availability of water.

Wet method

The wet method can be adopted in areas where water is available in plenty. Seedlings raised by the wet bed method can be harvested one week earlier. The seedbed should be prepared in advance, so that the pre-germinated seeds can be sown in time. As far as possible, fertile lands with irrigation and drainage facilities should be selected for raising the nurseries. Such lands should be suitably located to receive full sunlight. The following are the steps in raising wet nursery.

Plough and harrow the fields two or three times until the soil is thoroughly puddled and levelled. Prepare raised beds 5 to 10 cm high 1 to 1.5 m wide and of convenient length with drainage channels between the beds. The total seedbed area should be 1000 m2 for each hectare of the field to be transplanted.

Apply compost or cattle manure @ 1 kg per m2 of the nursery bed and mix well with the soil at the time of preparation of the field.

Treat the seeds by wet method. Drain and incubate in warm moist place for sprouting. Never allow the seeds to dry up. Moisten them occasionally. Sow germinated seeds on the third day. Delay will result in poor seedling stand.

Irrigation may be commenced on the 5th day after sowing and continued up to the 7th day, to a depth of about 5 cm. After this period, irrigate the seedbed continuously to a depth of about 5 cm in order to control weeds.

Drain occasionally to encourage production of vigorous seedlings with short roots. Flooding the soil with too much water for long periods produces tall and weak seedlings, which do not readily recover during transplanting.

If symptoms of nitrogen deficiency are observed, broadcast urea at the rate of 1 kg for 100 m2 as top dressing about 10 days prior to pulling out of seedlings, depending upon the duration of variety.

Dry method

This method is practised in areas where sufficient water is not available and the time of planting is uncertain. During first crop season, wherever transplanting is done depending upon receipt of rainfall, it is safer to adopt this method since growth of the seedlings can be controlled.

Plough the nursery area to a fine tilth. Prepare raised beds of 1 to 1.5 m width, 15 cm in height and of convenient length. Apply compost or cattle manure at the rate of 1 kg/m2 of the nursery bed and mix well with the soil at the time of preparation of the field.

Sow the seeds treated as described under dry seed treatment method, evenly over the bed and cover with fine sand / soil.

Water the nursery as and when required depending upon the receipt of rains.

Note: Rice seedlings from solarised nursery beds showed high initial growth, early maturity and resistance to leaf blast disease (ad hoc recommendation).

Age of seedlings

Seedlings are ready to be pulled out when they attain the stage of 4-5 leaves, about 18 days after sowing in the case of short duration varieties and 20-25 days after sowing in the case of medium duration varieties. Under ill drained conditions, the long duration varieties may be planted 30 days after sowing. Seedlings more than 30 days old when transplanted in the field recover slower than younger seedlings, especially, if they suffer stem and root injury. However, during the virippu season, age of seedlings can go up to 35 days in case of medium duration varieties and 25 days for short duration varieties. If the seedlings are over aged, plant at a closer spacing with 3 or 4 seedlings per hill and apply extra dose of nitrogen @ 5 kg/ha as basal dressing.

Irrigate seedbeds a day before pulling out the seedlings to soften the soil and to facilitate washing of roots.  Wash off mud and soil from the roots carefully and tie the seedlings into bundles of convenient size for transplanting.

Pruning of the top portion and root is not recommended as it inflicts wounds through which disease causing organisms may subsequently enter.

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